Release coatings are well known in the pressure sensitive adhesive tape industry to provide a release surface so that a tape can be unwound from a roll without the adhesive sticking to the backside of the tape. The release coating can also be coated onto a liner which serves as a carrier for a pressure sensitive adhesive transfer tape or a double coated tape, both of which are tacky on both sides of the tape.
Materials commonly used for release surfaces and coatings are silicone compositions because they can be formulated to provide varying levels of release from a "premium" release (i.e., the force to unwind the tape is very low) to a "low adhesion backsize" release which typically requires a greater force to unwind.
The primary deficiency of silicone release coatings is the potential contamination that may be associated with them. When workers handle a silicone release coated tape or liner, silicone can transfer to their hands, work gloves, or clothing. The silicone can be further transferred from their hands to surfaces to be painted, and cause problems such as poor adhesion of the paint to the contaminated surface, and nonwetting of the paint in areas where the silicone is present on the surface. Silicone release materials also tend to be costly, and silicone coated materials may be difficult to recycle.
Polyethylene has also been used as a release material and can be coated onto Kraft papers for a release liner or it can be used as a single layer film, or a multi-layer film with polyethylene co-extruded with or laminated to a base layer such as high density polyethylene, and the like. Higher density polyethylenes are limited in use to certain adhesives and are found to be unsuitable for very aggressive pressure sensitive adhesives because the adhesion between the polyethylene and the adhesive is so high that it can be difficult to start removing the liner. Since the release force is high, the adhesive and/or the liner can also be damaged as one tries to separate the adhesive from the liner.
There remains an ongoing need for controlled release liners for pressure sensitive adhesives that do not have a silicone release layer.